This invention relates to pneumatic tools in general, and more particularly to improved forms of pneumatic fastening tools.
Pneumatic fastening tools per se are not new in the art. Various examples of such tools are shown in U.S. Pat. Nos. 4,122,904, 4,098,171, 4,040,554, 3,498,577, 3,905,535, 3,776,445, 3,512,454 and 3,708,096 and the references cited therein. These tools typically comprise a housing, a cylinder disposed in the housing, a piston slidably mounted in the cylinder, a hammer connected to the piston, means for causing the piston to reciprocate within the cylinder so as to drive the hammer from a first retracted position to a second extended position, and a nozzle section for receiving a fastener and positioning it for engagement with the hammer in order to permit the hammer to drive the fastener from the nozzle into a workpiece.
It is sometimes desired that the fastening tool be used to attach small articles such as washers or name tags to the workpiece. Some tools known to be in use require the tool operator to manually position the small metal member against the workpiece and hold it there by hand or some other means while he fastens it on. This fastening technique is not satisfactory when the member being attached is small in size (thereby making it difficult and dangerous to manually hold the member in place during fastening) or when the member being attached is a washer which has a small center hole to be penetrated and therefore requires critical fastening alignment. Efforts have been made to provide tools which have means for supporting the article to be fastened so that it will be suitably secured to a workpiece by a fastener driven by the tool. However, in certain cases there still exists the need for the operator to be able to manipulate the tool into engagement with the workpiece without subjecting himself to excessive strain or risk of losing his balance and incurring injury from a fall. It also may be essential that the operator not come into contact with the workpiece in cases where the workpiece is excessively hot. The latter requirement exists in the steel industry where it is desired to attach metal identification tags to hot steel ingots or to attach insulation liners to the inside surfaces of molds used in casting steel ingots. In this connection it is well known in the steel industry that undesired large voids may appear in an ingot if premature solidification takes place in the region of the upper edges of the mold while the mold is still being filled or while the metal in the center of the mold is still molten. The typical method of preventing this solidification is to apply a liner of suitable insulation, generally available in the industry under the names Hot-Top and Riser, to the inside surface of the mold at its upper end. The insulation acts to prevent heat loss through the mold at its upper end, thereby assuring that the melt will not prematurely freeze in the mold. The preferred manner of attaching the insulation to the mold is to fasten it on by means of nail-like fasteners, with the point of the fastener penetrating the insulation and fixing itself in the wall of the mold and the head or shank of the fastener engaging a washer which in turn engages the insulation liner and holds it firmly against the mold.
Such a fastening technique involves certain obvious requirements. First of all, very high power impact drivers are required to set the fasteners. Second, the impact drivers must be mobile and relatively light in weight in order to reduce operator fatique and allow rapid advancement of the tool along the workpiece. Third the drivers must be arranged so that they can contact the work without bringing the operator in contact with the work or placing him in a precarious position. This latter problem is complicated by the fact that some fastening operations may be at waist-height while others may be at or below the level of the operator's feet. Fourthly the drivers must be designed to prevent accidental operation.
Explosive-activated impact drivers do not satisfy these requirements since they are relatively slow in operation, expensive, dangerous to operate, and suffer from substantial noise and recoil problems. Furthermore, the design and mode of operation of such tools presents significant problems to utilizing these tools around the large (e.g. 5'.times.4'.times.10') cast iron molds previously described, with operators sometimes being required to work in an awkward or tiring position when attaching the insulation to the mold.
As a result, one of the objects of the present invention is to provide a device for attaching insulation to cast iron molds which is substantially free of the problems facing explosive-activated impact tools.
Another object is to provide means for making it more convenient to use a fastener driver of the type shown in U.S. Pat. No. 4,040,554 for attaching insulation to cast iron molds.
Yet another object is to provide a fastening device which has a high degree of mobility and a unique handle and trigger extension for using the tool in hard-to-reach locations. Still another object is to provide a tool of the type described which has operating mechanisms providing a relatively high degree of safety against accidental operation.
Still another object is to provide a tool which is adapted to attach a member to a very hot workpiece, such as a newly cast steel ingot, without the operator having to place his hand next to the workpiece, thereby reducing the risk of operator injury.
A further specific object is to provide a tool of the type described which has an extension handle and embodies control means which prevent it from driving a fastener until it is engaged with a workpiece. Another specific object is to provide a pneumatic driver which cannot be operated unless the operator uses both hands and until the driver is engaged with a workpiece.
Still another specific object is to provide a relatively light weight pneumatic driver of the type described which features a light weight poppet valve of sturdy yet simple construction.